Investigation of Flexible Sweat Sensor for Sodium-Ion Concentration with a Combination of Two Sensing Mechanisms

We present a flexible microelectrode array for analyzing the NaCI electrolyte of the sweat of human beings based on two sensing mechanisms. The sensor is fabricated on polyimide (PI) substrate which is low-cost, flexible, and biocompatible as the wearable application for healthcare monitoring. Based on the electrolyte impedance measurement transduction, the two adjacent microelectrodes show a linear response with a sensitivity of 8.78 mS/M to the electrolyte concentration of human sweat range from 10 to 120 mM. In comparison with the impedance method, the open-circuit potential (OCP) measurements are carried out with a modified ion-selective electrode versus a commercial reference electrode. The OCP results show the rational Nernst response (66.2 mV/decade) in a range of 10−5~10−1 M and with the limit of detection (LOD) of 8.2×10-6 M.